[Haskell-cafe] performance difference for binary-0.4.3.1 with ghc-6.8.3 and ghc-6.10

[Don Stewart]

jwlato:
> Hello,
> 
> I was experimenting with using ghc-6.10.0.20081007 on a project, and
> it seems that binary-0.4.3.1 has markedly worse performance in certain
> cases.  With the following simple test:
> 
> > import qualified Data.ByteString.Lazy as L
> > import Data.Binary
> > import Data.Binary.Get
> > import Control.Monad
> >
> > main :: IO ()
> > main = do
> >     b <- L.readFile "some_binary_file"
> >     putStrLn $ show $ runGet getter b
> 
> > getter :: Get [Word16]
> > getter = replicateM 1000000 getWord16le
> 
> running this program compiled with ghc-6.10 takes about 4 times as
> long (and consumes much more memory) as when compiled with ghc-6.8.3.
> The extra time appears to be proportional to the number of elements
> processed in the Get.  Running the programs with -hT shows a clear
> memory difference, which I think is the source of the problem.  I've
> placed pdfs of that output at https://webspace.utexas.edu/latojw/data/
> 
> The difference seems to manifest itself only when the elements are
> actually processed; changing "show $ runGet " to "show $ length $
> runGet " is slightly faster in 6.10.
> 
> I was working on an Intel Mac with OS 10.4, binary-0.4.3.1, and
> bytestring-0.9.1.4.  Can anyone confirm this, or suggest what might be
> the difference?
> 

Is this the sole test case?

I can investigate. Though perhaps using a newer GHC release candidate is
also a good idea.

-- Don